Method of making magnetic head with precisely defined zero throat height

ABSTRACT

A method makes a magnetic head having a top and a bottom, front and rear ends and an air bearing surface (ABS) at the front end, comprising the steps of forming first and second pole piece layers with the first and second pole piece layers separated by a write gap layer at the ABS and connected at a back gap that is recessed rearwardly in the head from the ABS; forming a zero throat height (ZTH) defining layer of baked photoresist that is sandwiched between the first and second pole piece layers with the ZTH defining layer having a rounded front edge where the first and second pole piece layers first separate from one another after the ABS to define the ZTH; and forming an insulation stack with a coil layer embedded therein between the first and second pole piece layers with the insulation stack placed so that the ZTH defining layer is located entirely between the ABS and the coil layer.

REFERENCE TO RELATED APPLICATION

This is a divisional application of application Ser. No. 09/138,307filed Aug. 21, 1998 now U.S. Pat. No. 6,134,080.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic head with a preciselydefined zero throat height (ZTH) and more particularly to a magnetichead that employs a thin strip of baked photoresist for defining theZTH.

2. Description of the Related Art

A merged magnetic head includes a write head portion and a read headportion. The write head portion includes a coil layer embedded in first,second and third insulation layers (called “the insulation stack”), theinsulation stack being located between first and second pole piecelayers. A gap is formed between the first and second pole piece layersby a gap layer at an air bearing surface (ABS) of the write head. Thepole piece layers are connected at a back gap. Current conducted throughthe coil layer produces a magnetic field in the pole pieces. Themagnetic field fringes across the gap at the ABS for the purpose ofwriting information in the form of magnetic impressions in tracks onmoving magnetic media, such as in circular tracks on a rotating magneticdisk or in longitudinal tracks on a moving magnetic tape.

The read head portion of the merged head includes a read sensor that issandwiched between first and second gap layers. The first and second gaplayers are sandwiched between first and second shield layers. The firstand second gap layers magnetically insulate the read sensor from theshield layers and the shield layers protect the read sensor from straymagnetic fields. The read sensor may be an anisotropic magnetoresistive(AMR) sensor or a spin valve sensor. In either instance a recessed edgeof the sensor is referred to in the art as the “stripe height” of theread head. This height is important because it establishes the magneticsof the read head. Flux signals traversing the sensor from a rotatingmagnetic disk causes a change in resistance in the sensor that isdetected by processing circuitry when a sense current is conductedthrough the sensor.

An important parameter in the design of the write head is the locationof the zero throat height (ZTH). The zero throat height is the locationwhere the first and second pole piece layers first commence to separatefrom one another after the ABS. Flux leakage between the first andsecond pole piece layers is minimized by locating the zero throat heightas close as possible to the ABS. Short zero throat heights have beenlimited by prior art methods of construction.

In the prior art, the forward sloping edge of one of the first, secondor third insulation layers of the insulation stack is employed fordefining the zero throat height. It is important that the zero throatheight be accurately located relative to the height of the stripe of theread head. When a partially completed merged head is lapped to thespecified air bearing surface the write head should have the desiredzero throat height and the stripe should have the desired stripe heightin order to satisfy the designed magnetics of the head. It is alsoimportant that the zero throat defining insulation layer have a forwardedge at the zero throat height that slopes at an appropriate angle,which is referred to in the art as the apex angle. The first insulationlayer of the insulation stack can be relatively thin which results in alow apex angle. In contrast the second insulation layer of theinsulation stack is a relatively thick layer which results in a higherapex angle. A higher apex angle, such as 35 degrees, is desirable forseveral reasons: (1) a lower apex angle results in more flux leakagebetween the first and second pole piece layers and (2) a lower apexangle results in more variability (windage) in the location of theforward edge of the zero throat defining insulation layer due tosubsequent processing steps.

Each insulation layer of the insulation stack is constructed ofphotoresist. Photoresist is spun on and planarzed across a wafer wheremultiple magnetic heads are to be constructed. For each head, thephotoresist is photopatterned by light imaging so as to prepare portionsof the photoresist for removal by developing. The photoresist is thendeveloped leaving a photoresist layer with desired openings. Thephotoresist layer is then baked at a high temperature which causes it toshrink and solidify. Each of the insulation layers of the insulationstack is constructed one on top of the other commencing with the firstinsulation layer.

The longer the insulation layer the more the forward edge of theinsulation will recess into the head due to shrinkage of the layer. Whenthe zero throat defining insulation layer is the first insulation layerof the insulation stack it is subjected to process variations duringsubsequent construction of the coil layer. After the coil layer is frameplated a seedlayer is removed by sputter etching, ion milling or thelike which also etches or ion mills the forward edge of the firstinsulation layer. This causes the forward edge of the first insulationlayer to be relocated further into the head. A thin first insulationlayer causes the forward edge of the layer to have a low apex angle.Unfortunately, etching or ion milling removes more of the forward edgeof the layer when the apex angle is small because the full height of thelayer is further back in the head. As stated hereinabove a low aspectangle also causes more flux to leak between the first and second polepiece layers.

When the second or third insulation layer of the insulation stack isselected for the zero throat defining insulation layer the forward edgehas a higher aspect angle which is more favorable for reducing fluxleakage between the first and second pole tip layers. Further the secondand third insulation layers are not subject to etching or ion millingsince they are constructed after construction of the coil layer.Unfortunately, however, the second or third insulation layers can berelatively thick and shrinkage during baking causes the forward edge ofthe insulation layer to be further recessed in the head than when thefirst insulation layer is used as the zero throat defining layer.

Accordingly, defining the zero throat height with any of the insulationlayers of the insulation stack has not been satisfactory. The windage orrelocation of the forward edge of the selected insulation layer duringconstruction has made the exact location of the zero throat heightunpredictable. The relative location of the zero throat height to thestripe height after lapping is then uncertain. There is a strong feltneed for construction of the zero throat height insulation layer thatresults in a more predictable location and aspect angle of the forwardedge of the layer.

SUMMARY OF THE INVENTION

The present invention provides a photoresist insulation layer thataccurately locates the zero throat height of a magnetic write head witha highly predictable aspect angle at a forward edge of the insulationlayer. This is accomplished by employing a discrete photoresist stripthat is decoupled from the large mass of any of the first, second orthird photoresist insulation layers of the insulation stack. Thephotoresist strip, which is located entirely between the ABS and aforward end of the coil layer, has a predetermined width as it extendsfrom a forward sloping edge toward the back gap. Since the width of thephotoresist strip is many orders of magnitude less than the length ofany of the insulation layers of the insulation stack, shrinkage of thephotoresist strip during the baking step is minimal. Accordingly, thelocation of the forward edge of the photoresist strip imaged during thelight exposure step is virtually the location of the forward edge of thephotoresist strip after the baking step. This greatly promotes thepredictability of the zero throat height thereby achieving twosignificant advantages, namely: (1) locating the zero throat heightcloser to the ABS and (2) more accurately placing the zero throat heightwith respect to the stripe height of the read head. These advantagesequate to improved data rates and more data stored and read by themagnetic head per square inch of the magnetic disk. Accordingly, themagnetic disk drive, which is the heart of a computer, is enabled toprovide still more gigabits of stored information for the user withoutany increase in physical size of the disk drive.

The other important advantage of the photoresist strip is that the apexangle of the forward sloping edge of the photoresist line can beoptimized with great predictability. The apex angle is directly relatedto the ratio of the thickness of the photoresist layer spun on the waferto the width of the photoresist strip imaged during the light step. Thisratio is referred to in the art as the aspect ratio. Accordingly, theaspect angle is increased by increasing the thickness of thephotoresist. A desirable aspect angle, such as 35°, is easily achievableand predictable by spinning a sufficiently thick photoresist layer onthe wafer, photopatterning and developing the layer and then hard bakingthe layer. An aspect angle of 35° minimizes flux leakage between thefirst and second pole piece layers.

The present invention is manifested in various embodiments. In oneembodiment the photoresist strip is totally separate from a firstphotoresist layer of the insulation stack. In another embodiment, thefirst photoresist layer of the insulation stack is provided with anelongated hole that defines the photoresist strip. In a furtherembodiment the coil layer is moved forward in the head by placing thefirst turn of the coil layer in the elongated hole. In still furtherembodiment a photoresist layer accurately and predictably defines thezero throat height as well as planarizing the partially completed headwith respect to the first pole piece layer.

An object of the present invention is to provide a magnetic head withphotoresist that more accurately defines a zero throat height.

Another object is to provide a photoresist layer for a magnetic headthat more accurately and predictably defines the zero throat height andaspect angle of a write head.

A further object is to provide a process of making a merged head thatmore accurately and predictably locates the zero throat height of awrite head relative to a stripe height of a sensor of a read head.

Still another object is to provide a first photoresist insulation layerof an insulation stack that also provides a thin strip of photoresistforward of a coil layer for accurately and predictably defining a zerothroat height and apex angle.

Still a further object is to provide the foregoing object as well aspositioning a coil layer closer to the ABS than heretofore obtainable inthe prior art.

Still another object is to provide a photoresist insulation layer thatis planarized with respect to a first pole piece layer and that providesan accurate and predictable zero throat height and apex angle.

Other objects and advantages of the invention will be more readilyappreciated upon reading the following description taken together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of an exemplary magnet disk drive:

FIG. 2 is an end view of a slider with a magnet head of the disk driveas seen in plan 2—2;

FIG. 3 is in elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the magnetic taken along plan 5—5 of FIG. 2;

FIG. 6 is an enlarged partial view front portion of the slider and aprior art magnetic head as seen in plane 6—6 at FIG. 2;

FIG. 7 is a partial view of the slider and the prior art magnetic headas seen in plane 7—7 at FIG. 6;

FIG. 8 is a view taken along plane 8—8 of FIG. 6 with all material abovethe coil layer removed;

FIG. 9 is an enlarged partial side view of the slider and magnetic headof the present invention as seen in plane 9—9 of FIG. 2;

FIG. 10A is a partial plan view of a partially completed head showingthe present photoresist strip for defining the zero throat height of thewrite head;

FIG. 10B is a view taken along plane 10B—10B of FIG. 10A;

FIG. 10C is the same as FIG. 10B except a first insulation layer (I1)has been formed;

FIG. 11A is a plan view of a partially completed head showing theelongated photoresist strip of the present invention defined by anelongated hole in the first insulation layer of the insulation stack ofthe head;

FIG. 11B is a view taken along plane 11B—11B of FIG. 11A;

FIG. 11C is the same as FIG. 11B except the magnetic head has beencompleted.

FIG. 12A is a plan view of a portion of a partially completed headshowing the elongated photoresist strip of the present invention asdefined by a hole in the first insulation layer of the insulation stack;

FIG. 12B is a view taken along plane 12B—12B of FIG. 12A;

FIG. 12C is the same as FIG. 12A except a second insulation layer ofinsulation stack has been formed;

FIG. 12D is a view taken along plane 12D—12D of FIG. 12C;

FIG. 12E is the same as FIG. 12A except a coil layer, shownschematically as a line, has been formed;

FIG. 12F is a view taken along plane 12F—12F of FIG. 12E;

FIG. 12G is the same as FIG. 12F except the magnetic head has beencompleted;

FIG. 13A is a plan view of a portion of another partially completedmagnetic head embodiment of the present invention;

FIG. 13B is the same as FIG. 13A except a write gap layer and a coillayer have been formed;

FIG. 13C is a view taken along plane 13C—13C of FIG. 13B;

FIG. 13D is the same as FIG. 13C except the magnetic head has beencompleted;

FIG. 14A is a plan view of a portion of still another embodiment of apartially completed head of the present invention;

FIG. 14B is a view taken along plane 14B—14B of FIG. 14A;

FIG. 14C is the same as FIG. 14A except a coil layer has been formed;

FIG. 14D is a view taken along plane 14D—14D of FIG. 14C;

FIG. 14E is the same as FIG. 14D except the magnetic head has beencompleted;

FIG. 15A is a plan view of a portion of still another embodiment of apartially completed magnetic head of the present invention showing theformation of a plannerizing layer adjacent the first pole piece layer;

FIG. 15B is similar to FIG. 15A except a zero throat height defininginsulation layer strip has been formed to define the zero throat heightof the magnetic head;

FIG. 15C is the same as FIG. 15B except a coil layer has been formed;

FIG. 15D is a view taken along plane 15D—15D of FIG. 15C;

FIG. 15E is the same as FIG. 15D except the magnetic head has beencompleted; and

FIG. 16 is a block diagram of exemplary steps employed in making thepresent magnetic head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views there is illustratedin FIGS. 1-3 a magnetic disk drive 30. The drive 30 includes a spindle32 that supports and rotates a magnetic disk 34. The spindle 32 isrotated by a motor 36 that is controlled by a motor controller 38. Acombined read and write magnetic head (merged magnetoresistive or spinvalve head) 40 is mounted on a slider 42 that is supported by asuspension 44 and actuator arm 46. A plurality of disks, sliders andsuspensions may be employed in a large capacity direct access storagedevice (DASD) as shown in FIG. 3. The suspension 44 and actuator arm 46position the slider 42 so that the magnetic head 40 is in a transducingrelationship with a surface of the magnetic disk 34. When the disk 34 isrotated by the motor 36 the slider is supported on a thin (typically,0.05 μm) cushion of air (air bearing) between the surface of the disk 34and the air bearing surface (ABS) 48. The magnetic head 40 may then beemployed for writing information to the form of magnetic impressions tomultiple circular tracks on the surface of the disk 34, as well as forreading information in this form of magnetic impressions (bit)therefrom. Processing circuitry 50 exchanges signals, representing suchinformation, with the head 40, provides motor drive signals for rotatingthe magnetic disk 34, and provides control signals for moving the sliderto various tracks. In FIG. 4 the slider 42 is shown mounted to thesuspension 44. The components described hereinabove may be mounted on aframe 54, as shown in FIG. 3.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. Theslider has a center rail 56 that supports the magnetic head 40, and siderails 58 and 60. The rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of the magnetic disk 34, the cross rail 62 isat a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

Prior Art Merged Magnetic Head

FIG. 6 is a side cross-sectional elevation view of the merged head 40which has a prior art write head portion 70 and a read head portion 72,the read head portion employing a sensor 74. FIG. 7 is an ABS view ofFIG. 6. The sensor 74 is located between first and second gap layers (G1and G2) 76 and 78 and the gap layers are located between first andsecond shield layers (S1 and S2) 80 and 82. In response to externalmagnetic fields, the resistance of the sensor 74 changes. A sensecurrent I_(s) conducted through the sensor causes these resistancechanges to be manifested as potential changes. These potential changesare then processed as readback signals by the processing circuitry 50shown in FIG. 3.

As shown in FIG. 6, the write head portion of the merged head includes acoil layer 84 located between first and second insulation layers (I1 andI2) 86 and 88. A third insulation layer (I3) 90 may be employed forplanarizing the head to eliminate ripples in the second insulation layercaused by the coil layer 84. The first, second and third insulationlayers are referred to in the art as an “insulation stack”. The coillayer 84 and the first second and third insulation layers 86, 88 and 90are located between first and second pole piece layers 92 and 94. Thefirst and second pole piece layers (P1 and P2) 92 and 94 aremagnetically coupled at a back gap 96 and have first and second poletips 98 and 100 which are separated by a write gap layer (G3) 102 at theABS. As shown in FIGS. 2 and 4, first and second solder connections 104and 106 connect leads from the sensor 74 to leads 112 and 114 on thesuspension 44 and third and fourth solder connections 116 and 118connect leads 120 and 122 from the coil 84 (see FIG. 8) to leads 124 and126 on the suspension. A wear layer 128 may be employed for protectingthe sensitive elements of the magnetic head, as shown in FIGS. 2, 4, 6,and 7. It should be noted that the merged head 50 employs a single layer82/92 to serve a double function as a second shield layer for the readhead and as a first pole piece for the write head. A piggyback MR heademploys two separate layers for these functions.

The Invention

In FIG. 9 a first embodiment 200 of the present invention isillustrated. The magnetic head 200 employs an elongated photoresiststrip 202 which has been hard baked to provide the photoresist strip 202with first and second substantially parallel elongated edges 204 and206. The forward and rear edges 204 and 206 slope upwardly with theslope of the forward edge having an apex angle α. The forward edge 204defines the zero throat height (ZTH) of the magnetic head. Thephotoresist strip 202 has a width W between its forward and rear edges204 and 206 which is preferably located entirely between the ABS and thefirst turn of the coil layer 84.

FIGS. 10A, 10B and 10C illustrate the various steps in the constructionof the first embodiment shown in FIG. 9. After the formation of thefirst pole piece layer 82/92 and the gap layer 102, the photoresiststrip 202 is formed transverse the head as shown in FIG. 10A. FIG. 10Bis longitudinal cross section through FIG. 10A. FIG. 10C is the same asFIG. 10B except the fist insulation layer 86 of the insulation stack hasbeen formed. As shown in FIG. 10C, the photoresist strip 202 has a firstportion 208 which extends from the forward edge 204 to a forward edge210 of the first insulation layer and a rear portion 212 which extendsfrom the forward edge 208 of the first insulation layer to the rear edge206. From FIG. 10C it can be seen that the first insulation layer 86covers the rear portion 212 of the photoresist strip 202 and from FIG. 9it can be seen that the second and/or the third insulation layers 88 and90 and the second pole piece layer 94 cover the forward portion 208 ofthe photoresist strip 202.

FIG. 16 is an exemplary method of construction of the magnetic head 200shown in FIG. 9. As shown in FIGS. 9 and 16, after constructing the readhead portion of the magnetic head, which includes formation of the firstpole piece layer 82/92, a write gap layer 102 is formed on the firstpole piece layer 82/92. The write gap layer 102 etched at a back gapregion as shown at 96 in FIG. 9, so that the second pole piece 94 can besubsequently connected to the first pole piece 82/92. Next a layer ofphotoresist is spun on the write gap layer 102. The photoresist layer isthen photopatterned to prepare portions of the photoresist layerselected for removal by developing. The photoresist layer is thendeveloped leaving the photoresist strip 202 between the ABS site and thecoil site of the partially completed head. After the photoresist layerhas been developed, the photoresist strip is baked at a hightemperature, such as 270° C., which causes the photoresist strip 202 toslightly shrink and produce the sloping surfaces extending from theforward and rear edges 204 and 206. It should be realized that theshrinkage of the very narrow photoresist strip is many orders ofmagnitude less than the shrinkage of any one of the insulation of theinsulation layers stack which, in the prior art, was employed fordefining the zero throat height. In other words, the baking step resultsin a minimal movement of the forward edge 204 back into the headcompared to the movement of the forward edge of the first insulation orany other insulation layer of the insulation stack back into the head.Accordingly, the very narrow photoresist strip of the present inventionenables more accurate and predictable zero throat heights. This isimportant in establishing the designed positional relationship betweenthe zero throat height and the stripe height 214 of the read head asshown in FIG. 9.

Further, by varying the thickness of the photoresist layer and/or thewidth W of the photoresist strip, the apex angle α can be moreaccurately defined with improved predictability. The thickness of thephotoresist strip is approximately the thickness of the photoresistlayer spun onto the partially completely head. The ratio of thethickness of the photoresist layer to the width of the photoresist stript÷W which is referred to in the art as the apex ratio. The apex angle αis directly proportional to the aspect ratio. An increase in the aspectratio produces an increase in the apex angle α. Accordingly, if thethickness of the photoresist layer is increased the apex angle α isincreased. A preferred apex angle α is 35° which will minimize fluxleakage between the first and second pole piece layers immediatelybehind the zero throat height. The width of the strip 202 may be on theorder of 3-8 microns (μm). Next the insulation stack is formed with oneor more coil layers. The insulation layers of the insulation stack haveopenings at the back gap region so that when the second pole piece isformed it makes connection with the first pole piece 82/92 as shown inFIG. 6.

FIG. 11A illustrates another embodiment 300 of the invention wherein thefirst insulation layer 302 of the insulation stack is employed forproviding the photoresist strip 304. As shown in FIG. 11B, the gap layer306 is formed on the first pole piece layer 308. The first insulationlayer 302, which is a photoresist, is then formed on the gap layer 306with an elongated opening 310. The elongated opening 310 forms the rearedge of the elongated strip 304. The first insulation layer 302 is madeby spinning a photoresist layer onto the partially completely head andphotopatterning the photoresist layer for removal of photoresist at theopening layer 310 for forming a periphery which defines the zero throatheight (ZTH) and for providing an opening at the back gap discussedhereinabove. The patterned photoresist layer is thin baked which causesthe sloping surfaces of the photoresist strip 304 as shown in FIG. 11B.The advantages of the embodiment 300 in FIG. 11A over the embodiment 200in FIG. 9 is that the first insulation layer 302 of the insulation stackand the photoresist strip 304 can be made with one layer of photoresist.Next, the coil layer 312 is formed, as shown in FIG. 11B, followed bycompletion of the insulation stack 314 and the second pole piece layer216 as shown in FIG. 11C.

FIG. 12A illustrates a further embodiment 400 of the present inventionwherein a first insulation layer 402 of the insulation stack alsoprovides the photoresist strip 404. This is accomplished by providingthe first insulation layer 402 with an opening 406 which is slightlyspaced from outside edges of the first pole piece layer 408. The forwardedge 410 of the photoresist strip 404 defines the zero throat height ofthe head. As can be seen from FIG. 12B, the top surface of the firstinsulation layer 402 is substantially flush with the top surface of thewrite gap layer 412. The order of construction, shown in FIG. 12B, isformation of the first pole piece layer 408, formation of the write gaplayer 412, etching the write gap layer to provide an opening 413 at theback gap and then formation of the first insulation layer 402 along withthe photoresist strip 404. In FIGS. 12C and 12D, a second insulationlayer 414 of the insulation stack is formed with a via at 413. In FIGS.12E and 12F a coil layer 416 is formed on the second insulation layer414 and in FIG. 12G the remainder of the magnetic head is completed byforming the remainder of the insulation stack 418 with a via at 413 andthe second pole piece layer 420.

FIGS. 13A through 13D illustrate still another embodiment 500 of thepresent invention. This embodiment is similar to the embodiment 400,shown in FIG. 12A, except the first insulation layer 502 is spaced fromthe sides edges of the first pole piece 504 by the write gap layer 505(See FIG. 13D). The photopatterning of the photoresist layer providesthe opening 506 which partially encompasses a back portion of the firstpole piece layer 504 behind the photoresist strip 508. Accordingly, whenthe opening 506 is provided in the first insulation layer, thephotoresist strip 508 is formed with a forward edge 510 which definesthe zero throat height of the magnetic head. As shown in FIGS. 13B and13C, the order of construction is formation of the write gap layer 505on the first pole piece layer 504 with an opening or via at the back gapregion, followed by formation of the first insulation 502 along with thephotoresist strip 508 on the write gap layer and the opening 506 whichexposes the via 511. The coil layer 514 is then formed followed bycompletion of the insulation stack 516 with vias at 511 and the secondpole piece layer 518 to complete the head as shown in 13D.

FIGS. 14A through 14D illustrate still a further embodiment 600 ofpresent invention. This embodiment is similar to the embodiment 300shown in FIG. 11A except the first insulation layer 602 of theinsulation stack is provided with a curved opening 604. The curvedopening 604 provides the photoresist strip 606 with a slightly curvedrear edge 608 and a substantially straight forward edge 610. As shown inFIGS. 14C and 14D, the forwarddmost turn 612 of the coil layer 614 isformed in the opening 604. The increased forward location of the coillayer 614 with respect to the ABS site is important for applying fieldto the first and second pole pieces as close as possible to the ABS soas to minimize flux leakage therebetween. The order of construction, asshown in FIG. 14D, is to form the first pole piece layer 614 followed bythe write gap layer 616. The first insulation layer 602 is then formedon the gap layer 616 along with the photoresist strip 606 followed byformation of the coil layer 614. The head is completed, as shown in FIG.14E, by forming the remainder of the insulation stack 618 followed byformation of the second pole piece layer 620.

FIGS. 15A through 15B illustrate still a further embodiment 700 of thepresent invention. In this embodiment a planarizing layer 702 is formedadjacent the side and back of the first pole piece layer 704 as shown inFIG. 15A. The top surface of the planarizing layer 702 is preferablysubstantially flush with the top surface of the first pole piece layer704 as shown in FIGS. 15A and 15D. As shown in FIG. 15B, a write gaplayer 708 is formed on top of the first pole piece 704 and theplanarizing layer 702 with a via at 705 and the photoresist strip 706may be formed on top of the write gap layer 702. If desired the writegap layer 708 can be formed prior to the planarizing layer 702 in whichcase the planarizing layer would be formed on top of the write gap layer708. As shown in FIG. 15E the magnetic head 700 is completed byformation of the coil layer 710 and the remainder of the insulationlayers of insulation stack 712 with vias at 709 followed by formation ofthe second pole piece layer 714. The planarizing layer 708 may beomitted if the first pole piece layer 704 is formed with sufficientwidth to support the entire width of the front located turns of the coillayer.

It should be appreciated that the present invention provides aphotoresist strip which enables accurate placement of the zero throatheight with high predictability. This enables the zero throat height tobe located, as designed, with respect to the strip height of the sensorof the read head portion of the head. Further, the photoresist stripenables the construction of a desired aspect ratio for minimizing fluxleakage between the first and second pole piece layers. Photoresistmaterials comprehend a broad class of compositions. Generally, theinventions contemplate use of any material that acts like photoresist.Therefore, each of the aforementioned embodiments provide variousbenefits heretofore unobtainable in the prior art.

Clearly, the other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by followingclaims, which include all such embodiments and modifications when viewedin conjunction with the above specification and accompanying drawings.

We claim:
 1. A method of making a magnetic head having a top and abottom and front and rear ends and an air bearing surface (ABS) thatdefines the front end, comprising: forming first and second pole piecelayers with the first and second pole piece layers being separated by awrite gap layer at the ABS and connected at a back gap that is recessedrearwardly in the head from the ABS; forming a zero throat height (ZTH)defining layer of baked photoresist that is sandwiched between the firstand second pole piece layers with the ZTH defining layer having arounded front edge where the first and second pole piece layers firstseparate from one another after the ABS to define the ZTH; and formingan insulation stack between the first and second pole piece layerswherein the insulation stack has at least first and second insulationlayers with at least one coil layer embedded therein and with theinsulation stacked placed so that the ZTH defining layer is locatedentirely between the ABS and the at least one coil layer.
 2. A method asclaimed in claim 1, further including: forming the ZTH defining layerwith front and rear portions; and forming a portion of the second polepiece layer directly on the front portion of the ZTH defining layer andforming a portion of the insulation stack directly on the rear portionof the ZTH defining layer.
 3. A method of making a magnetic head havinga top and a bottom and front and rear ends and an air bearing surface(ABS) that defines the front end, comprising the steps of: forming firstand second pole piece layers with the first and second pole piece layersbeing separated by a write gap layer at the ABS and connected at a backgap that is recessed rearwardly in the head from the ABS; forming a zerothroat height (ZTH) defining layer of baked photoresist that issandwiched between the first and second pole piece layers with the ZTHdefining layer having a rounded front edge where the first and secondpole piece layers first separate from one another after the ABS todefine the ZTH; forming an insulation stack between the first and secondpole piece layers wherein the insulation stack has at least first andsecond insulation layers with at least one coil layer embedded thereinand with the insulation stack placed so that the ZTH defining layer islocated entirely between the ABS and the at least one coil layer; andforming the ZTH defining layer directly on the write gap layer.
 4. Amethod as claimed in claim 3, further including: forming the ZTHdefining layer with front and rear portions; and forming a portion ofthe second pole piece layer directly on the front portion of the ZTHdefining layer and forming a portion of the insulation stack directly onthe rear portion of the ZTH defining layer.
 5. A method of making amagnetic head having a top and a bottom and front and rear ends and anair bearing surface (ABS) that defines the front end, comprising:forming first and second pole piece layers with the first and secondpole piece layers being separated by a write gap layer at the ABS andconnected at a back gap that is recessed rearwardly in the head from theABS; forming a zero throat height (ZTH) defining layer of bakedphotoresist that is sandwiched between the first and second pole piecelayers with the ZTH layer having a front end where the first and secondpole piece layers first separate from one another after the ABS todefine the ZTH; forming an insulation stack between the first and secondpole piece layers wherein the insulation stack has at least first andsecond insulation layers with at least one coil layer embedded thereinand with the insulation stacked placed so that the ZTH defining layer islocated entirely between the ABS and the at least one coil layer;forming the first insulation layer of the insulation stack of bakedphotoresist with a hole that divides the first insulation layer intofirst and second portions; and forming the first portion of the firstinsulation layer as said ZTH defining layer.
 6. A method as claimed inclaim 5, further including: forming the second portion of the firstinsulation layer with a top surface that is substantially planar; andforming said at least one coil layer directly on said top surface of thefirst insulation layer.
 7. A method as claimed in claim 5, furtherincluding: forming the hole so that the hole encompasses first andsecond side edges and a back end edge of a top surface of the first polepiece layer; forming the second insulation layer on the first insulationlayer and on the top surface of the first pole piece layer with asubstantially planar top surface that extends thereacross; forming saidat least one coil layer on a top surface of the second insulation layer;and said insulation layer including a third insulation layer whichcovers said at least one coil layer.
 8. A method as claimed in claim 7,further including: forming the ZTH defining layer with front and rearportions; and forming the second insulation layer with a front portionthat is located directly on the rear portion of the ZTH defining layerand the second pole piece layer with a front portion that is locateddirectly on the front portion of the ZTH defining layer.